1. Technology Field
The present invention generally relates to a flash memory storage system, and more particularly, to a flash memory storage system with a data protection function, and a controller and a data protection method thereof.
2. Description of Related Art
Smart cards have been broadly used along with the widespread of e-wallet and prepayment applications. A smart card is an integrated circuit (IC) card embedded with such components as a microprocessor, a card operating system, a security module, and a memory which allow a card holder to perform various predetermined operations. Besides the function of data storage, a smart card also offers calculation, encryption, bidirectional communication, and security functions such that data stored in the smart card can be protected. A subscriber identification module (SIM) card used in a GSM (Global System for Mobile Communications) cellular phone is one of the applications of smart card. Generally speaking, a smart card has very limited storage capacity due to the limited scales of ICs therein.
A memory card is a data storage equipment and which usually uses a NAND flash memory as its storage medium. A NAND flash memory is rewritable and erasable, and data stored in a NAND flash memory is retained even when no power is supplied to the NAND flash memory. In addition, along with the advancement of the fabricating technique, a NAND flash memory offers many other advantages, such as small volume, high access speed, and low power consumption, etc. Thus, in recent years, people in the industry have been trying to integrate smart card with large-capacity memory card in order to increase the storage capacity of smart card.
However, when a smart card and a memory card are integrated, security data is stored in the memory card but not in the original IC chip. Accordingly, how to ensure the security of data stored in the memory card is the key of whether the application can succeed. For example, if a user deposits $1000 in a smart card (for example, a prepaid card used in a shop) which uses a memory card as its storage medium and uses this smart card to make a payment, since the memory card is an independent circuit, the user can make a hard copy of the data in the memory card after the user determines the position of the memory card in the smart card. After the payment is made, the user can store the hard copy back into the memory card to refresh the value in the memory card. Thereby, how to protect the security of data in a flash memory is one of the most focused subjects in the industry.